Balloon catheter

ABSTRACT

A balloon catheter prevents detachment of a balloon from an inner shaft without using a conventional sleeve or heat-shrinkable tube. The balloon catheter includes a balloon, an inner shaft, and a tip having a proximal end portion that covers an outer periphery of a distal end of the balloon. The distal end of the balloon is sandwiched between the inner shaft and the proximal end portion of the tip, thereby joining the distal end of the balloon to the inner shaft and the tip.

CROSS REFERENCE TO RELATED APPLICATION

This is a Continuation of application Ser. No. 15/198,260 filed Jun. 30,2016, which in turn claims priority to Japanese Application No.2015-181288, filed on Sep. 15, 2015, the entire contents of which areincorporated herein by reference.

BACKGROUND

The disclosed embodiments relate to a medical device. Specifically, thedisclosed embodiments relate to a balloon catheter to be inserted into atarget site (such as a stenosis site) in a blood vessel in order toexpand the target site.

Balloon catheters for expanding stenosis sites and the like have alreadybeen proposed. A balloon catheter mainly comprises a balloon as aninflatable body; an outer shaft joined to a proximal end of the balloon;and an inner shaft inserted into the inside of the balloon and the outershaft. In the conventional balloon catheter, the balloon can be detachedfrom the inner shaft or the outer shaft at a joining portiontherebetween when the balloon is inflated. Various configurations havebeen proposed in order to solve this problem.

For example, U.S. Pat. No. 6,918,920 discloses a balloon catheter inwhich a distal tip is joined to a distal end of an inner tube; aproximal shaft portion of a balloon is joined to the inner tube; and theinner tube, the distal tip, and the proximal shaft portion of theballoon are joined by a sleeve.

Further, Japanese Patent Application Laid-Open No. 2009-056297 disclosesa balloon catheter in which a proximal end of a balloon is sandwichedbetween a tube body and a heat-shrinkable tube.

However, in the foregoing balloon catheter according to U.S. Pat. No.6,918,920, the proximal shaft portion of the balloon is merely joined toan outer periphery of the inner tube. Therefore, the balloon tends todetach from the inner tube when the balloon is inflated. Further,although the distal tip is joined to the distal end of the inner tubeand an inner periphery of the sleeve, the joining strength is notenough. Therefore, disadvantageously, the distal tip also tends to breakoff from the inner tube. Specifically, when the internal pressure isincreased in order to inflate the balloon, the proximal shaft portion ofthe balloon becomes susceptible to detachment from the inner tube. Whenthe internal pressure is further increased, the balloon and the innertube are forced to extend in the distal direction. This causes thesleeve to be pushed from the proximal end, which, in turn, makes thesleeve susceptible to detachment, and the distal tip may break off fromthe inner tube.

Furthermore, even if the foregoing heat-shrinkable tube disclosed inJapanese Patent Application Laid-Open No. 2009-056297 were used insteadof the foregoing sleeve in U.S. Pat. No. 6,918,920, the distal tip mightnonetheless break off from the inner shaft.

SUMMARY

Accordingly, an objective of the disclosed embodiments is to provide aballoon catheter in which a balloon is not easily detached from an innershaft, and breakage and detachment of a tip from an inner shaft can beprevented without using the conventional sleeve or heat-shrinkable tube.

A balloon catheter of the disclosed embodiments comprises a balloon, aninner shaft joined to a distal end of the balloon, and a tip joined to adistal end of the inner shaft, wherein the tip extends in the proximaldirection so as to cover an outer periphery of the balloon, and thedistal end of the balloon, the inner shaft, and the tip are joined suchthat the distal end of the balloon is sandwiched between the inner shaftand a proximal end portion of the tip.

According to the aforementioned configuration, the distal end of theballoon, the inner shaft, and the tip are joined such that the distalend of the balloon is positioned at a portion sandwiched between theinner shaft and the proximal end portion of the tip. Therefore, thedistal end of the balloon is not easily detached from the inner shaft.Further, since a conventional sleeve, heat-shrinkable tube, and the likeare not used, the number of components can be reduced as a whole.Furthermore, the joining strength between the tip and the balloon can beoptimized by adjusting the length and area of the balloon covered withthe tip. Therefore, a risk of breakage and detachment of the tip fromthe inner shaft can certainly be reduced.

Additionally, a configuration is described herein where an outerperiphery of the inner shaft has unevenness (i.e., an uneven surfacetopography) at a joining portion where the distal end of the balloon,the inner shaft, and the tip are joined. According to the aforementionedconfiguration, in a case where the unevenness is formed on the outerperiphery of the inner shaft at a place facing the distal end of theballoon, the joining area between the distal end of the balloon and theouter periphery of the inner shaft can be increased. As a result, thedistal end of the balloon is not easily detached from the inner shaft.For example, the distal end of the balloon is caught on the unevennessformed on the outer periphery of the inner shaft by virtue of ananchoring effect. Therefore, the distal end of the balloon is not easilydetached from the inner shaft even when a high pressure is applied tothe balloon.

A configuration is also described in which the unevenness on the outerperiphery of the inner shaft is formed by burying a coil body inside theinner shaft. In a case where the unevenness is formed by the outer shapeof the coil body as described above, an additional step of formingunevenness on the outer periphery of the inner shaft is not required.Therefore, the process for forming unevenness can be simplified.

Further, a configuration is described in which an inner periphery of thedistal end of the balloon at the joining portion has unevennesscorresponding to the unevenness of the outer periphery of the innershaft. According to the aforementioned configuration, the joining areabetween the distal end of the balloon and the outer periphery of theinner shaft can be further increased. As a result, the distal end of theballoon is even more resistant to detachment from the inner shaft.

Advantageously, in the balloon catheter according to the disclosedembodiments, the balloon is not easily detached from the inner shaft,and breakage and detachment of the tip from the inner shaft can beprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cross-sectional top view of a balloon catheteraccording to the disclosed embodiments.

FIG. 2 shows an enlarged partial cross-sectional view of the ballooncatheter shown in FIG. 1.

FIGS. 3A-3C show enlarged longitudinal sectional views of disassembledcomponents of the balloon catheter of FIG. 1 (FIG. 3A: a tip; FIG. 3B:an inner shaft; and FIG. 3C: a balloon).

FIG. 4 shows an enlarged partial cross-sectional view of a ballooncatheter according to the disclosed embodiments.

FIG. 5 shows an enlarged partial cross-sectional view of the ballooncatheter shown in FIG. 4.

DETAILED DESCRIPTION OF EMBODIMENTS

Balloon catheters according to the disclosed embodiments will bedescribed in detail. However, the present invention shall not be limitedto the embodiments described below, and modifications in design can bemade appropriately. In FIGS. 1 to 5, the left side corresponds to thedistal end, which is to be inserted into the body, and the right sidecorresponds to the proximal end, which is to be operated by an operatorsuch as a physician.

For example, FIG. 1 shows a balloon catheter 10 that may be used fortreating a stenosis site in a blood vessel of the heart, for example.The balloon catheter 10 comprises a balloon 20A, an outer shaft 30, aconnector 40, an inner shaft 50A, a tip 60, and a core wire 90.

The balloon 20A functions to expand the stenosis site, and comprises aresin material. In addition, a distal end 22A of the balloon 20A isjoined to a distal end of the inner shaft 50A and the tip 60, and aproximal end 23 of the balloon 20A is joined to a distal end of theouter shaft 30. Note that a joining structure of the distal end 22A ofthe balloon 20A will be described in more detail below.

The outer shaft 30 functions to supply a fluid to the balloon 20A, andcomprises a tubular member constituting an inflation lumen 36 forsupplying the fluid. Further, the outer shaft 30 has a distal end outershaft portion 31, a guide wire port portion 33, a middle outer shaftportion 35, and a proximal end outer shaft portion 37 in that order fromthe distal end. The distal end outer shaft portion 31, the middle outershaft portion 35, and the inner shaft 50A are joined at the guide wireport portion 33.

The inner shaft 50A is inserted into the distal end outer shaft portion31, and the inflation lumen 36 is formed between the distal end outershaft portion 31 and the inner shaft 50A. Further, the proximal endouter shaft portion 37 comprises a metal tubular member referred to as aso-called hypotube. In addition, a distal end of the proximal end outershaft portion 37 is inserted into and joined to a proximal end of themiddle outer shaft portion 35. Further, the connector 40 is attached toa proximal end of the proximal end outer shaft portion 37. Therefore,when a fluid for inflating the balloon 20A (such as a contrast agent andphysiological saline) is supplied through an indeflator (not shown) tobe attached to the connector 40, the fluid flows into the balloon 20Athrough the inflation lumen 36 to inflate the balloon 20A.

Note that the distal end outer shaft portion 31 and the middle outershaft portion 35 are each preferably a tube comprising a resin such as apolyamide, polyamide elastomer, polyolefin, polyester, or polyesterelastomer. Further, the proximal end outer shaft portion 37 preferablycomprises stainless steel (SUS 304) or a superelastic alloy such as aNi—Ti alloy.

The inner shaft 50A forms a guide wire lumen 51 for inserting a guidewire (not shown) thereinto. Further, a proximal end of the inner shaft50A is joined to the guide wire port portion 33 of the outer shaft 30 toform a proximal end guide wire port 54. Furthermore, a distal end guidewire port 69 is formed at the tubular tip 60 arranged at the distal endof the inner shaft 50A.

Moreover, a marker member 70 having a cylindrical shape is arranged atan outer periphery of the inner shaft 50A in the inside of the balloon20A.

The inner shaft 50A preferably comprises a resin such as a polyethylene,polyurethane, polyamide, polyamide elastomer, polyolefin, polyester, orpolyester elastomer. The tip 60 is preferably formed with a soft resinsuch as polyurethane or polyurethane elastomer. Moreover, the markermember 70 preferably comprises a radiopaque metal material such asplatinum or tungsten.

Further, the core wire 90 is attached to an inner periphery of thedistal end of the proximal end outer shaft portion 37. The core wire 90has a circular cross section, and is formed of a tapered metal wirematerial with a diameter that decreases toward the distal end. Inaddition, the core wire 90 extends through the middle outer shaftportion 35, the guide wire port portion 33, and the distal end outershaft portion 31. Further, the core wire 90 has a pressing member 92near a proximal end of the guide wire port portion 33. Thus, when apushing force and a rotating force are applied to the core wire 90, thepressing member 92 contacts the guide wire port portion 33, transmittingthe pushing force and the rotating force to the distal end outer shaftportion 31 and the inner shaft 50A.

Below, the joining structure at the distal end 22A of the balloon 20Awill be described with reference to FIGS. 2 to 3C.

As shown in FIG. 2, the distal end 22A of the balloon 20A is sandwichedbetween the inner shaft 50A and the tip 60, joining the distal end 22Aof the balloon 20A to the inner shaft 50A and the tip 60. According tothe aforementioned joining structure, detachment of the distal end 22Aof the balloon 20A from the inner shaft 50A can be prevented.

More specifically, as shown in FIGS. 2 and 3A, an inner surface of thetip 60 includes a step portion 62 with which the distal end 22A of theballoon 20A and the distal end of the inner shaft 50A make contact.Further, the tip 60 comprises a tip distal end portion 61 having atapered shape and extending from the step portion 62 toward the distalend guide wire port 69, and a tip proximal end portion 64 having atapered shape and extending from the step portion 62 toward the proximalend. Note that an inner periphery of the tip proximal end portion 64 onthe side of the inner shaft 50A corresponds to a tip proximal endjoining inner surface 65.

Furthermore, as shown in FIGS. 2 and 3B, the inner shaft 50A has atubular inner layer 55, a metal coil body 56 sparsely wound around anouter periphery of the inner layer 55, and an outer layer 57 formed overthe coil body 56. Moreover, the outer shape of the coil body 56 that isburied in the inner shaft 50A forms unevenness on an outer periphery 58a of the distal end of the inner shaft 50A.

Further, as shown in FIGS. 2 and 3C, an inner periphery of the distalend 22A of the balloon 20A that faces the inner shaft 50A corresponds toa balloon distal end joining inner surface 25 a, and the unevenness isformed on the balloon distal end joining inner surface 25 a. Inaddition, the balloon distal end joining inner surface 25 a ispre-formed so as to correspond to the unevenness on the outer periphery58 a of the distal end of the inner shaft 50A.

Further, as shown in FIG. 2, in a state where the distal end of theinner shaft 50A and the distal end 22A of the balloon 20A make contactwith the step portion 62 of the tip 60, the balloon distal end joininginner surface 25 a of the distal end 22A of the balloon 20A makessurface contact with the outer periphery 58 a of the inner shaft 50A onwhich unevenness is formed, and the outer periphery 24 of the distal end22A of the balloon 20A is covered with the tip proximal end portion 64of the tip 60, and the distal end 22A of the balloon 20A, the innershaft 50A, and the tip 60 are joined.

Here, a joining portion 80A corresponds to a portion where the distalend 22A of the balloon 20A, the inner shaft 50A, and the tip 60 arejoined with each other. Therefore, even when a fluid is introduced intothe inside of the balloon 20A to inflate the balloon 20A, and a stressis created for separating the distal end 22A of the balloon 20A from thedistal end of the inner shaft 50A, detachment of the balloon 20A fromthe inner shaft 50A can be prevented because the distal end 22A of theballoon 20A is covered with the tip proximal end portion 64.

Further, the tip 60 is integrally formed from the tip distal end portion61 of the distal end guide wire port 69 through the tip proximal endportion 64. Therefore, breakage and detachment of the tip 60 from theinner shaft 50A can be prevented.

Moreover, the joining portion 80A described above comprises the balloon20A, the inner shaft 50A, and the tip 60, and other materials are notrequired. Therefore, the number of required components is minimized.Further, since the tip 60 (including the tip distal end portion 61 andthe tip proximal end portion 64) has a tapered shape, the tip distal endportion 61 and the tip proximal end portion 64 can expand a stenosissite in a blood vessel in a radial direction when the balloon catheter10 is inserted into the stenosis site. Further, the tip proximal endportion 64 covers the distal end 22A of the balloon 20A, reducing therisk of the balloon 20A getting damaged by contact with the stenosissite. As a result, when a fluid is introduced into the balloon 20A,there is a reduced a risk of the balloon 20A rupturing.

Further, since the balloon distal end joining inner surface 25 a of theballoon 20A and the outer periphery 58 a of the inner shaft 50A eachhave corresponding unevenness in surface contact with each other, thejoining area is increased, obtaining an anchoring effect. Therefore,detachment of the distal end 22A of the balloon 20A from the inner shaft50A can be much more effectively prevented.

The unevenness on the outer periphery 58 a of the inner shaft 50A may beformed as follows: a molten resin is applied to the coil body 56arranged on the inner layer 55, and then cured to form an outer layer 57having unevenness. The unevenness is exposed on the outer periphery ofthe outer layer 57. Therefore, advantageously, an additional step forforming the unevenness is not required, and the number of manufacturingsteps is minimized.

A joining portion 80B of a balloon catheter 11 of the disclosedembodiments will be described with reference to FIG. 4. Note that thesame reference numbers are assigned to structures similar to those inthe preceding figures, and the descriptions thereof are omitted.

In FIG. 4, a monolayer inner shaft 50B is used instead of the innershaft 50A of FIGS. 1, 2, and 3B, and the joining portion 80B comprisesthe tip 60, the distal end 22A of the balloon 20A, and the inner shaft50B. Further, unevenness is formed on an outer periphery 58 b of theinner shaft 50B. Therefore, again according to the aforementionedconfiguration, detachment of the distal end 22A of the balloon 20A fromthe inner shaft 50B; breakage and detachment of the tip 60 from theinner shaft 50B; and damage to the balloon 20A upon insertion into astenosis site can be reduced without requiring additional components.

A joining portion 80C of a balloon catheter 12 according to thedisclosed embodiments will be described with reference to FIG. 5. Notethat the same reference numbers are assigned to structures similar tothose in the preceding figures, and the descriptions thereof areomitted.

In FIG. 5, a monolayer inner shaft 50C is used instead of the innershaft 50A used in FIGS. 1, 2, and 3B, and the joining portion 80Ccomprises the tip 60, a distal end 22C of a balloon 20C, and the innershaft 50C. Further, an outer periphery 58 c of the inner shaft 50C isformed so as to have a smooth surface without unevenness. A balloondistal end joining inner surface 25 c of the balloon 20C is also formedso as to have a smooth surface without unevenness. Even with the smoothsurface, detachment of the distal end 22C of the balloon 20C from theinner shaft 50C; breakage and detachment of the tip 60 from the innershaft 50C; and damage to the balloon 20C upon insertion into a stenosissite can be reduced without requiring additional components.

Note that other modifications can be made to the disclosed embodimentsin addition to as the modifications described above. For example, theunevenness on the outer periphery 58 a, 58 b of the inner shaft 50A, 50Bis not limited to a coil-like unevenness corresponding to the shape ofthe coil body 56 wound sparsely. The unevenness may be embossed suchthat a depressed portion and a protruding portion are provided at agiven interval, or the unevenness may be intermittently formed along theaxial direction of the inner shaft 50A, 50B. Further, the unevenness onthe outer periphery 58 a of the inner shaft 50A may be formed from thecoil body 56 that is completely buried in the inner shaft 50A, but theconfiguration is not limited to this. For example, (a) the outerperiphery of the coil body 56 may be partially exposed at the outerperiphery 58 a of the inner shaft 50A so that both the coil body 56 andthe outer layer 57 form unevenness on the outer periphery 58 a of theinner shaft 50A, or (b) the unevenness on the outer periphery 58 a ofthe inner shaft 50A may be formed from the coil body 56 and the innerlayer 55 without using the outer layer 57.

Further, in the balloon catheter 10, 11, 12, a wide range of dimensionsand shapes may be suitably selected for each component. Therefore, forexample, the length of the tip proximal end portion 64 of the tip 60along the axial direction of the tip 60, the thickness of the tip 60 inthe radial direction, and the like can be freely adjusted, therebyoptimizing the joining strength between the tip 60, the distal end 22A,22C of the balloon 20A, 20C, and the inner shaft 50A, 50B, 50C.

Further, in FIGS. 2 and 3B, the coil body 56 having a rectangularcross-sectional shape is wound around the outer periphery of the innerlayer 55, but the configuration is not limited to this. Thecross-sectional shape of a wire of the coil body 56 may be circular,elliptical, or polygonal. Further, the wire of the coil body 56 is notlimited to a metal wire, and a wire comprising a resin such as polyetherether ketone (PEEK) may also be used. Furthermore, a braid in whichmultiple wires are woven in a mesh-like manner may also be used insteadof the coil body 56.

What is claimed is:
 1. A balloon catheter comprising: a balloon; anouter shaft; an inner shaft joined to a distal end of the balloon; and atip having: a step portion provided on an inner surface thereof andconfigured to come in contact with the entire distal surface of theinner shaft; and a proximal end portion that covers an outer peripheryof the distal end of the balloon, wherein the distal end of the balloonis sandwiched between the inner shaft and the proximal end portion ofthe tip.
 2. The balloon catheter according to claim 1, wherein an outerperiphery of the inner shaft has an uneven surface topography at ajoining portion in which the distal end of the balloon, the inner shaft,and the tip are joined.
 3. The balloon catheter according to claim 2,wherein the uneven surface topography defines depressed portions andprotruding portions spaced at regular intervals.
 4. The balloon catheteraccording to claim 2, wherein the uneven surface topography definesdepressed portions and protruding portions spaced at irregularintervals.
 5. The balloon catheter according to claim 2, wherein theinner shaft is a monolayer inner shaft.
 6. The balloon catheteraccording to claim 2, wherein an inner periphery of the distal end ofthe balloon at the joining portion has an uneven surface topographycorresponding to the uneven surface topography of the outer periphery ofthe inner shaft.
 7. The balloon catheter according to claim 2, wherein:the inner shaft comprises a coil body; and the uneven surface topographyof the outer periphery of the inner shaft corresponds to the shape ofthe coil body.
 8. The balloon catheter according to claim 7, wherein aninner periphery of the distal end of the balloon at the joining portionhas an uneven surface topography corresponding to the uneven surfacetopography of the outer periphery of the inner shaft.
 9. The ballooncatheter according to claim 7, wherein the proximal end portion of thetip extends further in the direction of a proximal end of the ballooncatheter relative to a distal end of the coil body.
 10. The ballooncatheter according to claim 7, wherein the coil body is buried insidethe inner shaft.
 11. The balloon catheter according to claim 7, whereinthe coil body is partially buried inside the inner shaft and partiallyexposed.
 12. A balloon catheter comprising: a balloon; an outer shaft;an inner shaft joined to a distal end of the balloon; and a tip having:a step portion provided on an inner surface thereof, formed by a changein thickness of the tip, and configured to come in contact with a distalend of the inner shaft; and a proximal end portion that covers an outerperiphery of the distal end of the balloon, wherein the distal end ofthe balloon is sandwiched between the inner shaft and the proximal endportion of the tip.
 13. The balloon catheter according to claim 12,wherein the step portion provided on an inner surface of the tip isconfigured to come in contact with the entire distal surface of theinner shaft.
 14. The balloon catheter according to claim 12, wherein:the inner shaft comprises a coil body, an outer periphery of the innershaft has an uneven surface topography, corresponding to the shape ofthe coil body, at a joining portion in which the distal end of theballoon, the inner shaft, and the tip are joined, and an inner peripheryof the distal end of the balloon at the joining portion has an unevensurface topography corresponding to the uneven surface topography of theouter periphery of the inner shaft.
 15. The balloon catheter accordingto claim 12, wherein: the inner shaft comprises a coil body that ispartially buried inside the inner shaft and partially exposed, and anouter periphery of the inner shaft has an uneven surface topography,corresponding to the shape of the coil body, at a joining portion inwhich the distal end of the balloon, the inner shaft, and the tip arejoined.